The invention relates to an electronic musical instrument using a novel technique enabling a major part of a musical sound generating section to be constructed by digital circuitry.
Analog technology has dominantly been used in the field of electronic musical instruments such as electronic organs, electronic pianos and musical synthesizers, but digital technology which has recently made a marked advance, has also been used partly in this field.
A tremendously complicated control is necessary to fabricate a major part (a musical sound wave formation unit, a scale period formation unit, a unit for forming a curve tracing the positive-goings and the negative-goings of volume, and the like) in the music sound producing stage of an electronic musical instrument, by large scale integrated circuit (LSI) technology on the basis of the digital technology. However, no electronic musical instrument with a simple construction, resulting from a full application of the digital technology to the musical instrument construction, has successfully been developed.
In electronic musical instruments, the formation of various musical sound waves is of great importance for the purpose of producing the musical sounds having various timbre. For this, many proposals for designating the musical sound waves have been made. In one of the proposals, sine waves ranging from a fundamental wave to higher harmonics with given orders are stored into a plurality of memories in the form of digital signals representing the amplitudes of the waves. When a musical sound is designated, sine waves with the related orders are selectively and simultaneously read out and then those sine waves read out are synthesized to form a specified waveform of musical sound. Another proposal parmanently stores digital signals representing fundamental waves such as a triangle wave, a sine wave, a rectangular wave and a saw-tooth wave in a waveform memory unit. An additional proposal is to store parmanently signals representing digitally or analogously given waves of musical sounds in a fixed memory.
In order to obtain an artificial musical sound wave fairly analogous to its original natural musical sound, not only an analogous musical sound is used but also a volume envelope including factors such as wave rises and wave falls must be superposed on the analogous musical sound. However, there have been no proposals to effectively superpose the volume envelope on the sound wave by the digital technology. The conventional superposition of the volume envelope has been made by the analog technology or by using a complex control circuit. Thus, the musical sound wave formation technique by the digital technology, which is well adapted for LSI fabrication, has not yet been established in this field. A waveform dependent on frequency spectrum (for example, a harmonic structure in an ordinary state) and a volume envelope ranging from a wave rise to a wave fall or damping are generally major factors to determine a timbre of a musical sound produced by a natural musical instrument. However, a timbre peculiar to the natural musical instrument is greatly influenced by other various factors, for example, time-variation of the harmonic structure arising from delay of higher harmonic components which are observed at the time of sound producing by the brasses. Subtle fluctuation of higher harmonics, noise superposition which is observed at the time of plucking the strings, rapid disappearing of higher harmonics at the damping. Therefore, the time-variation of the harmonic structure must be taken into consideration, in addition to the waveforms and the volume envelope, in order to eliminate dull and bold sound feeling produced by electrical signals of the electronic musical instrument and to obtain natural sound feeling of the electronic musical sound.
In a conventional electronic musical instrument, for example, an electronic organ, the harmonic structure is not changed every sound and a volume envelope is merely superposed on the simple musical sound waves. In another example that musical sounds of pianos or cembalos are previously preset, the musical sound wave produced is a single wave previously set. A synthesizer, which is a single sound instrument, changes a filtering frequency band with time through an analog filtering operation by using a voltage controlled type filter (VCF) or the like. The change direction of the frequency band is relatively simple, for example, "low frequency to high frequency" or "high frequency to low frequency". Accordingly, additional sound effect units are further needed for securing more natural sound feeling. The synthesizer of the type enabling a chord performance needs a filter and a sound effect means for each performance key. This leads to complexity and bulky of the circuit construction of the musical sound instrument, and expensiveness of its manufacturing cost.
The conventional electronic musical instrument employs the analogue technology for the time-variation problem of the higher harmonic structure. Direct application of the technology for the chord performance involves many problems to be solved. Thus, the present state of this art has not provided a satisfactory musical sound wave formation by the digital technology suitable for the LSI and with the harmonic structure being time-variable for each sound.
Let us consider the formation of scale periods. In electronic musical instruments, the sound source frequencies corresponding to performance keys are determined on the basis of a temperament scale. A called frequency dividing sound source system is generally used for the formation of the sound source frequencies. In the system, a reference clock frequency is frequency-divided by a plurality of stages of frequency dividing circuits. And the respective sound source frequencies are formed by selecting proper combinations of the frequency dividing ratios among the frequency dividing circuits. A desired waveform is read out from a musical sound wave memory, for example, by the sound source frequency corresponding to an actuated performance key. The conventional electronic music instrument is designed mainly for a single sound. The chord performance by simultaneous actuation of plural performance keys, therefore, requires scale period control circuits each for each performance keys for the parallel processing purposes. This results in a considerably large circuit construction. An alteration is conceivable in which a single scale period control circuit is used commonly for a number of performance keys and is used in a time-division fashion. In this case, since the resolution is 1/n for n performance keys, one time processing control is performed for n time operations for one performance key. Bear this in mind, when a scale period is set for each performance key and a musical sound is produced, a circuit construction designed is considerably complicated. Thus, there has been no practical scale period control apparatus by digital technology which is simple in construction and well fits for the chord performance. This is also true for the digital processing system permitting the chord performance by plural-key actuation and the time-division dynamic processing in such a case.
Accordingly, an object of the invention is to provide an electronic musical instrument with a novel music sound generating technique implemented by the digital technology.
Another object of the present invention is to provide an electronic musical instrument in which a major part of the circuitry for producing musical sounds is substantially constructed by a digital circuit suitable for an LSI fabrication.
Still another object of the invention is to provide an electronic musical instrument which can form musical sound waves by a digital circuit implementing a novel technique.
A further object of the invention is to provide an electronic musical instrument in which the time-variation of a higher harmonic structure of musical sound is processed by the digital technology thereby to produce a musical sound with attractive timbre.
Still a further object of the invention is to provide an electronic musical instrument by using a novel technique capable of instructing simultaneously different waveforms.
An additional object of the invention is to provide an electronic musical instrument with a novel technique by which different waveforms may be simultaneously instructed and synthesized, and not only different waveforms but also the periods of different waves may be controlled to have M:N relation.
An even further object of the invention is to provide an electronic musical instrument with a novel technique which provides different volume envelope curves for different waveforms thereby to form a great variety of synthesized musical sound waveforms.
Another object of the invention is to provide an electronic musical instrument with a novel technique in which a scale period may be set by a digital counting control.
Yet another object of the invention is to provide an electronic musical instrument in which a chord performance is possible by digital dynamic processing technique.